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Dtr not running good


kenDAWG
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Well after the breaking in period of my top end rebuild my little dtr isn't running like it was...

I'll try to explain as best I can.

Bike pulls away perfect up to and beyond powerband 1st,2nd however I notice in 3rd its not revving up to the line a little hesitant then 4th is the same I can't open full throttle as I get a "burrrrrrwaaaahhhhhhh" like its wanting air drop off the throttle a little and away it pulls again same in 5th I don't even get into 6th as I can't get her into the powerband enough in 5th so 6th just drops off the revs.

I've cleaned out the petrol tap and fitted new washers etc, run through full tank of petrol with wurth 2 stroke additive, cleaned and oiled filter, decoked power valve and set her up, changed plug, cleaned carb and a few other bits and bobs

Am I running lean? Is it a case of adjusting the needle clip to richen it up a little?

It can't be the jets surely as the bike was running well before the topend rebuild!!!

Cheers

Ken

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Have you checked the float height. Stuff like this can happen if its a little low.

Fuel isnt filling the bowl fast enough. As you get further through the gears the fuel draw will increase.

The worn bore would have pulled less air through the carb. So it may not have shown as a problem enough to notice.

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Just been out on it there!

3rd gear doing about 30mph I roll the throttle 1/2 turn and and just bogs and starts juddering off the throttle than give her a little turn of the throttle increasing slowly no problems...

I'm sure its running lean I really can't be arsed with this crap.

Before I done the topend there was a rattle that's why I freshened her up, small end bairings where on there way out the rest was fine checked the bore etc and it still had cross hatching and no marks what so ever but I changed them any way!

Ken

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What makes you so sure its lean.

My dt went lean. ( dodgy inlet manifold that i didnt spotctill too late) and to be honest it had never run so well. I was loving the way she rode right up to the point that a hole you could drop a 5p through appeared in the piston.

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It's just the information I have been picking up of the Internet!

My air box has been butchered by previous owner as well-rather than a slot in the top where the snorkel goes the top has been opened up!

Don't know where to bloody start!

Ken

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Some of the info I picked up

"On a 2-stroke - Riding in 3rd gear, with a warm engine and the throttle BARELY cracked open, roll the throttle to 1/2. If the bike sputters and crackles, and you feel like you have to keep rolling on the throttle to smooth it out, the needle is too rich. If, on the otherhand, you get the dreaded 'buhhhhhhwaaaaa', the needle is too lean"

I for one am not confident enough to mess with jets and I haven't got the time with the bairn teething I only have limited time and I fill that with checking oils and cleaning her!

Could be a trip to westgate road for me there is a garage there who specialise in 2 smokers says he will tune the carb for £35

Ken

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Yes thats 4stroking when rich and flat when lean. Seriously you cannot tune a carb in 2 minutes. Given the price of labour these days for 35 quid he will probably stare at it. And give you it back.

Your just missing something simple. Engines are never identical. They all have there little differences. Hell there are 38 tractor units in our depot. All identical spec but every one drives different.

First job.

Check for leaks. Inlet or exhaust. Then to prove the basic theory ride a test route. 3 or 4 mile that you can repeat.

Now lift the needle one clip and go for a test. Better? No. Ok repeat with the cip the other way.

Let us know how you fare with that. Dont touch anything else just the needle height.

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Yeh that's the thing it isn't a 2 min job, I should have some spare time Sunday so ill get on it like a car bonnet!

I'm going for the clip to richen it, I've just sprayed up the exhaust and put her on no leaks ill just check the intak....

Normally a squirt of compressed air around the area can indicate air leak while engine is running.

What a chew on

Cheers for the help pal

Ken

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I'm with cynic try adjusting the needle, you don't need to pull the carb off to do it just rotate it in place to aloww the slide to be pulled out

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That is a good point lol-----/\

I would have had her in bits by now.

Will there be damage caused if this diagnosis is wrong?

Ill order a new spark plug and do a chop also

Cheers

Ken

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No doing this shouldn't cause any problems,just do your plug chop once you have it running right don't wan't to end up too lean,possibly you just need to adjust the air screw if lowering it makes it too lean then move it back and play with the air screw1/8 of a turn at a time.

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Turning the carb to the side was a no go!!!

Coolant inlet/outlet too short then there is that bottle ontop of the inlet needless to say everything else seems to go past either side of the carb and the fact the rubber from air box to carb has now decided to come out I have to strip the bike down a bit I managed to get to it but its too tight to put it all bak together.

I got the slide out and the needle clip was right on the top notch so I've dropped it one, once I get better access to the carb ill get it put back together

Cheers for the help

Ken

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Hmm sorry I would have thought it would be easier,if that don't do it your looking at a smaller main jet then. Your carb is heated by coolant?

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Now it won't fire up...

All I get it is a sound "tin tin blurgh".....

Choke on/off - little/no throttle - air box blocked up a little dam it I've drained through petrol to see if carb is filling up and yes it is.

Think ill have to put the clip back to normal then try air screw

Which way will richen mixture a little?

Cheers

Ken

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Urgh I get it all pulled back apart set the carb back then turn the key power valve cleaning cycle going slow and laboured!

Battery has decided its time for retirement, so I'm guessing when I changed the carb settings before and tried to start it the battery was at fault and not the settings.

So put the clip down one again and ordered a new gel battery so ill find out how it goes in a couple of days.

Grrrrrr pisses me off

Ken

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Yeh ken , do you know what main jet is in it, and the plug colour usually tells the story. January"s M.c.Mechanics. has a carb settup article by Stan stephens, great read, :yeah:

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